640123218 has 48 divisors (see below), whose sum is σ = 1587733056. Its totient is φ = 182584800.

The previous prime is 640123193. The next prime is 640123259. The reversal of 640123218 is 812321046.

640123218 is a `hidden beast` number, since 640 + 1 + 2 + 3 + 2 + 18 = 666.

It is a junction number, because it is equal to n+sod(n) for n = 640123191 and 640123200.

It is an unprimeable number.

It is a polite number, since it can be written in 23 ways as a sum of consecutive naturals, for example, 77068 + ... + 84968.

It is an arithmetic number, because the mean of its divisors is an integer number (33077772).

Almost surely, 2^640123218 is an apocalyptic number.

640123218 is an abundant number, since it is smaller than the sum of its proper divisors (947609838).

It is a pseudoperfect number, because it is the sum of a subset of its proper divisors.

640123218 is a wasteful number, since it uses less digits than its factorization.

640123218 is an evil number, because the sum of its binary digits is even.

The sum of its prime factors is 8559 (or 8556 counting only the distinct ones).

The product of its (nonzero) digits is 2304, while the sum is 27.

The square root of 640123218 is about 25300.6564736965. The cubic root of 640123218 is about 861.8291777000.

The spelling of 640123218 in words is "six hundred forty million, one hundred twenty-three thousand, two hundred eighteen".